The use of catheter delivery systems for positioning and deploying therapeutic devices, such as balloons, stents and embolic devices, in the vasculature of the human body has become a standard procedure for treating endovascular diseases. It has been found that such devices are particularly useful in treating areas where traditional operational procedures are impossible or pose a great risk to the patient, for example in the treatment of aneurysms in intracranial blood vessels. Due to the delicate tissue surrounding intracranial blood vessels, especially for example brain tissue, it is very difficult and often risky to perform surgical procedures to treat defects of intracranial blood vessels. Advancements in catheter deployment systems have provided an alternative treatment in such cases. Some of the advantages of catheter delivery systems are that they provide methods for treating blood vessels by an approach that has been found to reduce the risk of trauma to the surrounding tissue, and they also allow for treatment of blood vessels that in the past would have been considered inoperable.
Typically, these procedures involve inserting the distal end of a delivery catheter into the vasculature of a patient and guiding it through the vasculature to a predetermined delivery site. A vascular occlusion device may be attached to the end of a delivery member which pushes the occlusion device through the catheter and out of the distal end of the catheter into the delivery site. Some of the problems that have been associated with these procedures relate to the accuracy of occlusion device placement. For example, the force employed to effect detachment of the occlusion device from the delivery member may cause the occlusion device to over shoot the predetermined site or dislodge previously deployed occlusion devices. Also, once the occlusion device is pushed out of the distal end of the catheter it is advantageous for the occlusion device to be retrievable if repositioning or removal is needed. With current electro-thermal detachment systems, there have been instances where the tether members become reconnected to heating elements resulting in non-detachment. Non-detachment can result in adverse clinical complications particularly if multiple devices and being deployed. Premature detachment has also occurred in prior systems which can result in improper placement of a device and distal embolization which can cause and embolic stroke or other adverse clinical consequences.
Numerous devices and release mechanisms have been developed in an attempt to create delivery systems which provide both control of an occlusion device after the device has exited the delivery catheter and a rapid release or detachment mechanism to release the device once the occlusion device is in place with minimal or no force imparted to the implant. Further, there is a need to provide a system that has high reliability with low rates of both non-detachment and premature detachment. With some existing vascular release systems there is the potential to release undesirable particles of materials into the bloodstream that can also cause embolization in the bloodstream. There is therefore a need for a precise method of deploying therapeutic interventional devices without compromising the position of the implant, without causing thermal damage to surrounding tissues, and without releasing undesirable particles of materials into the bloodstream and risking the formation of emboli in the bloodstream.